This invention relates to an electronic concentration control system.
Closed loop electronic concentration control systems in which an exhaust gas composition sensor (e.g. a lambda sensor) located in an exhaust pipe sends a feedback signal to a calculation unit which generates as an output a concentration correction signal used to calculate the air/gasoline ratio (strength) of the mixture delivered to the engine are known.
In particular the correction signal may be used to modify an injection time Tj calculated using an open loop, e.g. by means of an electronic map, calculating a corrected injection time Tjcorr in a closed loop.
Systems which use first and second exhaust gas composition sensors located upstream and downstream of a catalytic converter respectively are also in existence. In these systems these first sensors are used in active mode to calculate the concentration correction signal while the second sensors generally perform a passive control function and are used to detect any abnormalities in the functioning of the first sensors.